1. Field of the Invention
The present invention relates to an inkjet print head used in an inkjet printing apparatus for ejecting a liquid such as ink to perform a print operation and a print element substrate for such an inkjet print head. It should be noted that the inkjet print head of the present invention may be applied not only to general printing apparatuses, but also to copying machines, facsimile machines with communication systems, apparatuses such as word processors with print units, or multifunction printers made of a combination with these apparatuses.
2. Description of the Related Art
The construction of the inkjet print head (hereinafter, simply called a print head also) used in the inkjet printing apparatus is disclosed in Japanese Patent Laid-Open No. H06-023997 (1994) or the like.
As the main component of the print head disclosed in Japanese Patent Laid-Open No. H06-023997 (1994), there is a print element substrate equipped with energy generating elements generating energy used for ejecting ink and a plurality of electrode terminals for supplying electrical signals to the energy generating elements. On the other hand, an electrical wiring substrate is connected to the print element substrate. The electrical wiring substrate is provided with an opening surrounding the print element substrate, connecting terminals (lead terminals) projecting into the opening to be connected to the electrode terminals of the print element substrate, connecting terminals receiving electrical signals including drive signals of print elements from an outside, and wiring transmitting electrical signals between these terminals. The print element substrate and the electrical wiring substrate are supported and fixed by a base member.
For example, in a print element substrate in the form of ejecting ink in a direction perpendicular to a main plane of the substrate, energy generating elements are formed on its surface and further, an ejection opening formation member in which ink ejection openings corresponding to the energy generating elements are formed is located thereon. An ink supply opening is provided so as to penetrate through both the front and back surfaces for supplying ink on the print element. The print element substrate is held in a state where the ink supply opening is in communication with an ink flow passage formation member from an ink tank in the back surface side. A peripheral side surfaces of the print element substrate are sealed by a sealant (first sealant), thus preventing leakage of the ink.
The electrical terminal of the print element substrate and the lead terminal of the electrical wiring substrate are electrically connected by a TAB mount technology and the electrical connecting portion is further sealed by a second sealant, thus protecting the connecting portion from corrosion due to ink or from external forces.
First, the first sealant is applied from the side portion of the print element substrate, then the first sealant gradually spreads along the peripheral side surfaces, and thereafter, spreads to the vicinity of the electrical connecting portion by a capillary force. The second sealant is to be applied mainly on the top surface of the electrical connecting portion after the first sealant is applied.
The lead terminal may be in contact with a portion on the print element substrate other than the electrode terminal of the print element substrate caused by external forces or defects of the lead terminal of the electrical wiring substrate. Therefore, Japanese Patent Laid-Open No. H06-023997 (1994) discloses a technology where of a barrier layer portion is provided in a portion positioned under a lead terminal extending portion to a lead terminal front end connected to the electrode terminal on the print element substrate, thus establishing electrical insulation between the lead terminal extending portion and the print element substrate.
By referring to FIGS. 13 to 15, the technology disclosed in Japanese Patent Laid-Open No. H06-023997 (1994) will be explained. FIG. 13 is a schematic plan view showing the connecting portion between the print element substrate and the electrical wiring member. FIG. 14 and FIG. 15 respectively are schematic cross sections taken along lines XIV-XIV and lines XV-XV in FIG. 13.
In each of the figures, reference symbols H1101 and H1105 denote a print element substrate and electrode terminals located thereon. Reference symbol H1109 denotes an ejection opening formation member in which ejection openings H1107 are formed. The ejection opening formation member H1109 is located on the print element substrate H1101 in a state where the ejection openings H1107 are aligned to the energy generating elements formed on the surface of the print element substrate H1101. Reference symbol H1301 denotes an electrical wiring substrate having an opening H1303 through which the print element substrate H1101 is exposed, Lead terminals H1304 are extend inside the opening H1303 and the front ends thereof are connected to the electrode terminals 1105. An integral barrier layer (insulating portion) 110 is provided in a portion positioned under the extensions of the lead terminals H1304 on the print element substrate 1101, where the barrier layer extends along an arrangement direction of the lead terminals H1304.
However, the construction disclosed in Japanese Patent Laid-Open No. H06-023997 (1994) has the problem as described below.
FIG. 16 will be used to explain this problem. The peripheral side surfaces of the print element substrate H1101 are sealed by the first sealant H1307, but at this time, the first sealant H1307 spreads to the connecting portion between the electrode terminal H1105 and the lead terminal H1304 for the sealing. However, in a case where the integral insulating portion 110 is provided along the arrangement direction of the lead terminals H1304 as Japanese Patent Laid-Open No. H06-023997 (1994), the first sealant H1307 which should spread to the vicinity of the electrical connecting portion by a capillary force may be blocked by the insulating portion 110. As a result, the first sealant is not sufficiently filled in a part of the electrical connecting portion, and therefore, a region where air bubbles exist or where the first sealant H1307 is not sufficiently filled may be left between the lead terminal H1304 and the print element substrate H1101 or between the lead terminals H1304.
When the second sealant is applied in a state where the region exists, in the heating process for sealant hardening as the process after the applying, the air may possibly inflate to be communicated with ambient air. Then, inflow of ink may occur, possibly deteriorating electrical reliability of the print head. In addition, a crack may be generated in the sealant by an external force applied at print operating after mounting the print head to the printing apparatus, possibly causing the deterioration of electrical reliability, similarly.